Process for bleaching sulfonic acids, esters and chlorides



United States Patent 2 Claims. (Cl. 260-456) This invention relates to the purification, or more specifically the bleaching of commercially prepared technical grade sulfonic acids or their derivatives.

,In the production of aliphatic or aromatic sulfonic acids and their derivatives, for example, the salts, chlorides, esters orarnides, strongly colored crude products are usually obtained. For bleaching these, the conventionaldecolorizing agents, for example, active carbon, bleaching earths silicic acid gel, hydrogen peroxide, sodium hypochlorite or sodium chlorite have been used hitherto. In general, it is necessary to repeat the treatmentwith these agents a number of times in order to obtain pure sulfonic acids, or relatively large amounts of decolorizing agent must be used. The color numbers serve as a measure of the purity. In this specification, the color numbers relate to the iodine color scale. The solutions are compared with solutions of iodine in water. The

color number means that the solution has a shade like that of an iodine solution which contains as many milligrams of iodine in 100 ml. of water asis indicated by thecolor number.

It is an object of this invention to provide a process for bleaching commercially prepared sulfonic acids or their derivatives in which a decolorizing agent is used which has not hitherto been used for this purpose. Another object of the invention is a process in which the decolorizing agent can be readily separated from the solutions which have been bleached therewith. A further object of the invention is a process in which with only a single treatment with a small amount of a decolorizing agent, sulfonic acids or theirfderivatives are obtained which have low color numbers.

These objects are achieved by treating commercially produced aliphatic or aromatiesulfonic acids or their salts, chlorides or esters are treated in the liquid phase, if desired in solution, with a small amount of a chlorinated cyanuric acid, preferably dior trichlorocyanuric acid, or an alkali salt of dichlorocyanuric acid.

The process may be used with aliphatic or aromatic sulfonic acids and their salts, the corresponding sulfonic acid chlorides and su'lfonic acid esters. Alkanesulfonic acids with 2 to 20 carbon atoms in the alkyl radical, alkenesulfonic acids with 2 to 20 carbon atoms in the alkene radical and arylsulfonic acids with one or two benzene rings in the aryl radical and with a total of 6 to'30 carbon atoms and also the corresponding salts, for example the alkali salts, the corresponding sulfonic acid chlorides and sulfonic acid esters are especially suitable. The alkyl, alkenyl and aryl radicals of the said sulfonic acids and sulfonic acid derivatives may contain groups which are inert under the reaction conditions, as, for example halogen atoms, such as chlorine, bromine, iodine or fluorine atoms, carboxyl groups or carboxylic acid ester groups the alcohol components of which contain 1 to 4 carbon atoms. When bleaching sulfonic acid esters, the alcohol of the ester grouping may be derived from aliphatic saturated alcohols with 1 to 20 carbon atoms or from, phenols with 6 to 20 carbon atoms. The following are given as examples of sulfonic acids and sulfonic acid derivatives which can be bleached according to this invention: ethylsulfonic acid, vinylsulfonic acid, octylsul- 3,232,975 Patented Feb. 1, 19 66 ice fonic acid, decylsulfo-nic acid, dodecylsulfonic acid, hexadecylsulfonic acid, eicosyl sulfonic acid, mixtures of alkylsulfonic acids such as are obtained byisaponification of sulfochlorides obtained by sulfochlorination of hydrocarbons with 8 to 12 or '16 to 20 carbon atoms, n-butenylsulfonic acid, dodecenyls'ulfonic acid, and 6-chloro-3-hex enylsulfonic acid, furthermore benzenesulfonic acidspthe various toluenesulfonic acids, p-tertiary-butylbenzenesulfonic acid, p-octylbenzenesul'fonic acid, padodecylbenzenesulfonic acid, OL- and fl-naphthalenesulfonic acid, diphenylsulfonic acid, sulfosuccinic acid, the various sulfobenzoic acids, the various sulfophthalic acids, sulfobenzenecarboxylic acidmethyl esters, sulfo-isophthalic acid dimethyl esters (benzenedicarbomethoxysulfonic acids), sulfo-isophthalic acid diethyl esters. All these sulfonic acids may also be used in the form of their salts, especially the alkali salts, for example, the sodium salt of ethylsulfonic acid, the potassium salt of octylsulfonic acid, the lithium salt of d-odecylsulfonic acid, the lithiur'n salt of hexadecylsulfonic acid, the sodium salt of benzenesulfonic acid and thepotassium salts of toluenesulfonic acids, the sodium salt of 5-sulfo-is ophthalic acid di methyl ester. The following are examples'of sulfonic acid chlorides: ethylsulfonic' acid chloride, 2-propene-l-sulfonic acid chloride, octylsulfonic acid chloride, dodecylsulfonic acid chloride, mixtures of sulfochlorides of long-chain alkanes such as are obtained by sulfochlorination of the'co rre sponding hydrocarbons, especially those derived from alkanes with 8 to :12 or 16 to 20 carbon atoms, further benzene sulfochloride, toluene sulfochlorides, naphthalene sulfochlorides,'B-chloroethane sulfochloride, 4-chloro benzene sulfochloride, and tert.-butylbenzene sulfochlorides The following are examples of sulfonic acid esters: ethylsulfonic acid ethyl ester, ethylsulfonic acid phenyl ester, octylsulfonic acid methyl ester, hexadecylsulfonic acid methyl ester, vinylsulfonic acid methyl ester, vinylsulfonic acid ethyl ester, vinylsulfonic acid phenyl ester, vinylsulfonic acid cresyl ester, benzylsulfonic acid methyl ester, toluenesulfonic acid butyl ester, naphthalenesulfonic acid ethyl ester, B-chloroethylsulfonicacid ethyl ester, fi-chloroethylsulfonic acid phenyl ester, dodecylsul-fonic acid phenyl ester, and ethylsulfonic 'acid -p-dodecylphenylester.

The process is especially suitable for bleaching alkylarylsulfonic acids with 4 to 12 carbon atoms in the alkyl group and one or two benzene rings, the alkali salt of these compounds, alkyl sulfonic acids with l2 to 20 carbon atoms and .the alkali salts of the latter compounds prepared on a technical scale.

The treatment of the sulfonic acid orits derivatives is effected by mixing orstirringvat a suitable temperature.

If the compounds to be bleached are liquid at room temperature, the treatment with the chlorinated cyanuric acids may be carried out directly. In the case of solid compounds, solutions are used, preferably those of 10 to 50% strength. Any inert solvents are suitable, but water is preferred. In manycases lower saturated aliphatic alcohols with 1 to 4 carbonatoms, such as methanol, ethanol, propanol and butanol, or lower aliphatic ketones with 3m 8 carbon atoms, such as acetone, are suitable. If, however, the compound to be bleached is not readily soluble in these solvents orundergoes c omplete or partial decomposition, other inert solvents are used, for examplelinear or cyclic ethers with 3 to 10 carbon atoms, for example diethyl ether, di-n-butyl ether, tetrahydrofuran and dioxane, or halogen hydrocarbons with l to 6 carbon atoms, such as carbon tetrachloride, chloroform and ethylene chloride, or nitriles of lower fatty acids with 2 to 6 carbon atoms, as :Eor example acetonitrile or propionitrile.

Pure dior tri-chlorocyanuric acid, alkali salts of dichlorocyanuric acid, for example, the sodium or potassium salt, or mixtures such as are formed by the chlorination of cyanuric acid, if desired in the form of the alkali salts, are used as bleaching agents. About 0.01 to 10% by weight, preferably 0.05 to 1%, of chlorinated cyanuric acid, is required with reference to the sulfo compounds. The amount to be used depends inter alia on the contents of active chlorine (for example, determinable iodometrically) in the chlorinated cyanuric acid (trichlorocyanuric acid has a content of active chlorine of 91.4%); when the content of active chlorine is high, for example 90%, a smaller amount is sufficient than with low contents, for example 69%.

Bleaching is carried out at below 100 C., preferably at temperatures between and 50 C.

The chlorinated cyanuric acids may be used solid or in solution, preferably in water or acetone, for example in the form of up to 2% aqueous solutions of trichlorocyanuric acid, up to 25% aqueous solutions of the sodium salt of dichlorocyanuric acid or up to aqueous so lutions of the potassium salt of dichlorocyanuric acid. A mixture with neutral extraneous substances, for example inorganic salts, detergents, cleansing agents or surfaceactive substances is also possible.

During the bleaching treatment, cyanuric acid is formed from the chlorinated cyanuric acids in the presence of water. Cyanuric acid is practically insoluble and can readily be separated in the usual way, for example by filtration with or without pressure or centrifuging. Usually, adequate separation can be effected even by decantation. Small amounts (about 0.1% per liter of aqueous solution) remain in the solutions of the sulfonic acids. This slight contamination is as a rule innocuous because cyanuric acid is substantially inert chemically.

The invention is illustrated by, but not limited to, the following examples in which parts are parts by weight. The bleaching effect is indicated by the color number (iodine color scale).

Example 1 0.20 part of dichlorocyanuric acid is added with efiicient stirring at 20 C. to 100 parts of a 30% aqueous solution of the trisodium salt of sulfo-isophthalic acid (initial color number 150). The Whole is heated to 60 C. in half an hour, kept at this temperature for another half hour, allowed to cool and after another half hour filtered. The solution then has the color number 2 to 3.

If only 0.05 part of dichlorocyanuric acid is used, a solution is obtained with the color number 12, and if 0.1 part is used, a solution with the color number 8 is obtained.

For purposes of comparison, the following are the results obtained with known decolorizing agents:

(a) With 1.0 part of aqueous sodium hypochlorite solution (12% active chlorine): color number 50;

(b) With 1.0 part of 30% hydrogen peroxide solution: color number 80 to 90;

(0) With 1.0 part of active carbon: color number 20 to 30;

(d) With 1.0 part of bleaching earth: color number 40 to 50.

Example 2 A 30% aqueous sulfo-isophthalic acid solution is bleached in a way analogous to that described in Example 1.

When using 0.2 part of dichlorocyanuric acid, the color number of the solution is improved from 200 to 5.

In comparative tests using 1.0 part of bleaching agent in each case, the following results are obtained:

Color number With sodium hypochlorite 71 With 30% hydrogen peroxide 65 With active carbon 33 With bleaching earth 55 4 Example 3 A 20% solution of tertiary-butyl-benzenesulfonic acid in methanol having the color number 200 is heated for an hour with 0.2 part of dichlorocyanuric acid at 35 C. After cooling and filtering the solution then has the color number 6.

Comparative experiments using known bleaching agents give the following results when 1.0 part per 100 parts of solution is used in each case:

Color number With sodium hypochlorite solution 44 With 30% hydrogen peroxide 62 With active carbon 41 With bleaching earth 74 Example 4 100 parts of a solution of 10 parts of 4-chlorobenzenesulfonic acid in 90 parts of water is intensely mixed by stirring for 2 hours at 50 C. with 0.05 part of the potas sium salt of dichlorocyanuric acid. The color number of the solution is improved from 210 to 13. In a comparative treatment with 1 part of 30% hydrogen peroxide solution, the color number is improved only to 46.

Example 5 100 parts of a solution of 15 parts of the sodium salt of p-dodecylbenzene sulfonic acid:

in 85 parts of water is stirred with 0.5 part of trichlorocyanuric acid for 3 hours at room temperature and the mixture heated to C., cooled and filtered. The color number of the solution is improved from more than 300 to 8. In an analogous treatment with 2 parts of active carbon, the color number is improved only to 57.

An analogous result is obtained by using the free acid instead of the sodium salt.

Example 6 100 parts of fi-chloroethanesulfonic acid chloride is stirred with 0.3 part of dichlorocyanuric acid for 2 hours. After filtration, fi-chloroethanesulfochloride with a color number of 15 is obtained, Whereas the initial material has a color number of more than 300. In an analogous treatment with 2 parts of active carbon, the color number is however improved only to 69.

Example 7 Example 8 100 parts of a solution of 15 parts of the sodium salt of 5-sulfo-isophthalic acid dimethyl ester:

([ZOOCHa NaOaS- COOJCHa and parts of water is stirred with 0.2 part of trichlorocyanuric acid for about half an hour at 55 C. After cooling, the solution is filtered. The color number of the solution is improved from 55 to 2. In an analogous treatment with 2 parts of active carbon only a color number of 18 is achieved.

Example 9 100 parts of a commercial alkylsulfochloride, obtained by sulfochlorination of a hydrocarbon mixture of- C to C -alkanes is kept at 20 to 40 C. for about half an hour while being stirred intensely with parts of a 1.0% aqueous solution of trichlorocyanuric acid. The aqueous phase is then separated. The color number of the alkylsulfochloride mixture is improved from 215 to 6. In a comparative treatment with 2 parts of active carbon, a color number of 66 is achieved.

If the alkylsulfonic acid chloride mixture is saponified with caustic soda solution, a mixture of the sodium salts of the alkylsulfon-ic acids is obtained. A 50% aqueous solution with the color number 49 is bleached to color numher 9 by treatment with 0.5 part of dichlorocyanuric acid for 2 hours.

Example 10 1.0 part of Water and 0.08 part of dichlorocyanuric acid are added to a solution or" 50 parts of benzene sulfochloride in 50 parts of butyl acetate with efiicient stirring. The mixture is stirred for an hour at room temperature. After separating the aqueous phase, the color number of the butyl acetate solution is improved from 71 to 5. In a comparative test with 1 part of bleaching earth, an improvement only to color number 18 is achieved.

Example 11 0.5 part of water and 0.1 part of dichlorocyanuric acid are introduced into 100 parts of fused 4-c'hlorobenzenesulfochloride at 56 C. while stirring well. After separating the cyanuric acid and the water, the color number of the 4-chlorobenzenesulfonic acid chloride has been improved from 88 to 11. In a comparative test with 2 parts of active carbon, a color number of only 30 is achieved.

Example 12 100 parts of an aqueous solution of 50 parts of a mixture of 90% ;3- and 10% a-naphthalenesulfonic acid in 50 parts of a 25% aqueous sulfuric acid is stirred with 0.3 part of the potassium salt of dichlorocyanuric acid for 3 hours at C. After filtration, the color number of the solution has been improved from more than 300 to 22; in a. comparative test with 2 parts of active carbon, a color number of only 90 is achieved.

Example 13 100 parts of a benzene solution containing 50 parts of p-chloroethane sulfonic acid p'henyl ester is stirred with 1.0 part of water and 0.5 part of dichlorocyanuric acid at 40 C. for 3 hours. The mixture is then filtered and dried. The color number of the solution is improved by this treatment from more than 300 to 18, whereas by treatment with 2 parts of active carbon a color number of only 39 is achieved.

I claim:

1. In a process for bleaching a sulfonic acid compound selected from the group consisting of alkane sulfonic acid with 2-20 carbon atoms, an alkene sulfonic acid with 2- 20 carbon atoms, an aryl sulfonic acid with 1-2 aromatic rings, an alkaryl sulfonic acid with 1-2 aromatic rings and not more than 30 carbon atoms, a sulfonic acid chloride of the aforesaid sulfonic acids, an alkali metal salt of the aforesaid sulfonic acids, a halogen-substituted alkene sulfonic acid with 2-20 carbon atoms, a halogensubstituted alkane sulfonic acid chloride with 2-20 carbon atoms, and an ester of the aforesaid sulfonic acids with an alcohol selected from the group consisting of an alkanol of 1-20 carbon atoms, phenol and an alkyl phenol having a total of not more than 20 carbon atoms, the improvement which comprises mixing said sulfonic acid compound With 0.01% to 10% by Weight, based on said sulfonic acid compound, of a chlorinated cyanuric acid compound selected from the group consisting of dichlorocyanuric acid, trichlorocyanuric acid, an alkali metal salt of dichlorocyanuric acid, and mixtures thereof, in a liquid phase for sufficient time to bleach the initial sulfonic acid compound.

2. A process as claimed in claim 1 wherein said sulfonic acid compound is a normally solid compound and is dissolved in an inert solvent before said mixing with said chlorinated cyanuric acid compound.

References Cited by the Examiner UNITED STATES PATENTS 2,185,864 1/1940 Muskat Ct a1 260553 2,607,738 8/1952 Hardy 260-248 XR 2,827,484 3/1958 Carlson Ct a1 260-505 2,828,308 3/1958 Lorenz 260 248 2,897,154 7/1959 Low 260 248 XR 2,913,460 11/1959 Brown 61 a1. 260 248 2,956,056 10/1960 Christian 260 248 OTHER REFERENCES Fierz-David et al., Jour. Soc. Dyers and Colourists, vol. 53, pp. 424-425 (1937), TP 890.86.

CHARLES B. PARKER, Primary Examiner. 

1. IN A PROCESS FOR BLEACHING A SULFONIC ACID COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKANE SULFONIC ACID WITH 2-20 CARBON ATOMS, AN ALKENE SULFONIC ACID WITH 220 CARBON ATOMS, AND ARYL SULFONIC ACID WITH 1-2 AROMATIC RINGS, AN ALKARYL SULFONIC ACID WITH 1-2 AROMATIC RINGS AND NOT MORE THAN 30 CARBON ATOMS, A SULFONIC ACID CHLORIDE OF THE AFORESAID SULFONIC ACIDS, AN ALKALI METAL SALT OF THE AFORESAID SULFONIC ACIDS, A HALOGEN-SUBSTITUTED ALKENE SULFONIC ACID WITH 2-20 CARBON ATOMS, A HALOGENSUBSTITUTED ALKANE SULFONIC ACID CHLORIDE WITH 2-20 CARBON ATOMS, AND AN ESTER OF THE AFORESAID SULFONIC ACIDS WITH AN ALCOHOL SELECTED FROM THE GROUP CONSISTING OF AN ALKANOL OF 1-20 CARBON ATOMS, PHENOL AND AN ALKYL PHENOL HAVING A TOTAL OF NOT MORE THAN 20 CARBON ATOMS, THE IMPROVEMENT WHICH COMPRISES MIXING SAID SULFONIC ACID COMPOUND WITH 0.01% TO 10% BY WEIGHT, BASED ON SAID SULFONIC ACID COMPOUND, OF A CHLORINATED CYANURIC ACID COMPOUND SELECTED FROM THE GROUP CONSISTING OF DICHLOROCYANURIC ACID, TRICHLOROCYANURIC ACID, AN ALKALI METAL SALT OF DICHLOROCYANURIC ACID, AND MIXTURES THEREOF, IN A LIUQID PHASE FOR SUFFICIENT TIME TO BLEACH THE INITIAL SULFONIC ACID COMPOUND. 